Multi-way doherty amplifier

Abstract

An electronic circuit has a multi-way Doherty amplifier. The multi-way Doherty amplifier comprises a two-way Doherty amplifier with a main stage and a first peak stage that are integrated in a semiconductor device; and at least one further peak stage implemented with a discrete power transistor.

Description

FIELD OF THE INVENTION[0001]The invention relates to an electronic circuit with a multi-way Doherty amplifier.BACKGROUND ART[0002]As known, a classical Doherty amplifier has two amplifying devices arranged in parallel and of the same power capability. The first one of the devices (main stage) operates in a class-AB amplifier mode and the second one (peak stage) operates in a class-C amplifier mode. These devices are separated at their inputs and at their outputs by 90° phase-shifting networks. The output phase-shifting network has a specific characteristic impedance Z0 which must be equal to the optimal load impedance RLm of the main stage. The input signal is split so as to drive the two amplifiers, and a summing network, known as an “impedance inverter” or a “Doherty combiner”, is operative to: a) combine the two output signals, b) to correct for phase differences between the two output signals, and c) to provide an inverted impedance at the output of the Doherty amplifier with re...

AI Technical Summary

Benefits of technology

The invention proposes an alternative approach for designing a multi-way Doherty amplifier. The integrated two-way Doherty amplifier is a pre-tested and optimized building block that is used as if it were a conventional discrete transistor. The design requires less design effort and takes up smaller space than a two-way design with discrete transistors. The integrated amplifier improves consistence in behavior and performance of a mass-produced amplifier. The design can be customized by choosing different components and sizes for the peak stage and main stage. The integrated amplifier also helps keep the main stage cooler, which increases its lifespan. The design can be further improved by arranging the amplifier and peak stage on the same metal flange in a push-pull package. This decreases the overall size of the amplifier and improves its consistence in mass production.

Problems solved by technology

However, designing a three-way Doherty amplifier that uses discrete transistors is a very time-consuming task and the quality or performance of such an amplifier is difficult to control in mass production.

Under laboratory conditions, a three-way Doherty amplifier shows superior efficiency at 12 dB back-off levels, but these amplifiers are not used on a large scale owing to the complexity of the design and the space needed to implement the design.

However, the design of a multi-way asymmetrical integrated Doherty amplifier, using the approach described in the publication of Blednov and van der Zanden, is a challenging task owing to the difficulties involved in properly dividing the input power between the main stage, the first peak stage, and the second peak stage and further in combining power outputs of several peak devices of different sizes in an MMIC (Monolithic Microwave Integrated Circuit) environment.

Also, the integrated two-way Doherty amplifier takes up smaller space than a two-way Doherty amplifier implemented with discrete transistors.

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